Injecting drug use is a major public health concern. Use of needles to inject drugs for non-medical reasons generally signifies a later stage of drug use as well as increased involvement in multiple drug use. It is associated with a number of health hazards. These health hazards not only include the drug-induced hazards such as drug dependence and overdose, but additionally the method-induced health hazards such as infections including hepatitis, endocarditis and HIV/AIDS. There has been an almost complete lack of research regarding the etiology of injecting drug use, and thus our knowledge of causes and risk factors of injecting drug use are limited. A few sporadic clinical studies have indicated that inhalant use might prove to be a modifiable risk factor or alternately an important vulnerability marker for injecting drug use. We used data compiled in the 1990 National Household Survey on Drug Abuse to test this association in an epidemiologic study, statistically adjusting for plausible confounders, including marijuana use. Based on multiple logistic regression models, respondents using both marijuana and inhalant were 88.1 times more likely to have injected drugs (95% confidence interval=123.7-62.7) than those who had neither used inhalants nor marijuana. Those using inhalants, but not marijuana were an estimated 45.3 times more likely to have injected drugs (95% CI=75.8-28.1). The odds ratio was 18.6 for those who had used marijuana, but not inhalants (95% CI= 25.-13.3). This study is a first step in understanding the etiologic conditions giving rise to injecting drug use.